Laser lamp failure detection method and means

ABSTRACT

Imminent failure of a lamp pump for a laser is anticipated by detecting a change in a physical dimension of the lamp normally occuring just prior to a failure. This change in physical dimension can be utilized to automatically terminate operation of the lamp.

I [1 1 [111 flfiZflIM Dehenedictis 1 Apr. III, I973 LASER ILA EUREDETECTION [56] References Cited METHOD AND ANS FOREIGN PATENTS ORAPPLICATIONS [75] Inventor: Leonard Charles Debenedictis, Los

Angeles, Calif 697,096 9/1953 Great Britain ..3l5/l I9 [73] Assignee:Union Carbide Corporation, New Primary Examiner.lohn Kominski Y k, N YAssistant Examiner-James B. Mullins Filed g 9 1971 Attorney-Pastoriza &Kelly 21 Appl. No.: 169,905 ABSCT Imminent failure of alamp pump for alaser is an- [52] cl l I i 315/107 315/119 ticipated by detecting achange in a physical dimen- [51] mm Cu H65) 41/36 sion of the lampnormally occuring just prior to a 58 d 6 119 failure. This change inphysical dimension can be util- 1 0 g/ ized to automatically terminateoperation of the lamp.

4 1w. 1 Drawing Figure 22 POWER SUPPLY y 2| INTERLOCK SWE'CH LIGHT PUP2O 4 EQUIP M E N T PATENHfI] APR 1 01975 3-, 7 27. 1 O1 I -22 POWERSUPPLY 2| INTERLOCK 23 SWITCH LIGHT PUMP 2O 24 EQUIPMENT 25 MICRO-SWITCH /l8 I 9 H 71m LASER LAMP T AlllLURE DETECTION METHOD AND MEANSThis invention relates to a method and means for detecting imminentfailure of a laser lamp pump such that operation of the lamp can beterminated prior to actual failure.

BACKGROUND OF THE INVENTION BRIEF DESCRIPTION OFTHE PRESENT INVENTIONWith the foregoing in mind, the present invention contemplates a methodand means for anticipating just such a failure thereby significantlyincreasing the value of lasers to the industrial community.

Moreparticularly, it is found that just preceeding a failure of thepumping lamp, a physical dimension of the lamp changes. In the specificcase of an elongated double based tungsten halogen lamp as used with YAGlasers, the lamp tube walls become soft just prior to failure and tendto expand diametrically if a compression is exerted at opposite ends. Inaccord with the invention such physical dimensional change is detectedand utilized to terminate operation of the lamp.

Ina specific embodiment for the tungsten halogen lamp, a mounting .isprovided which includes biasing means exerting a compressive force onthe two electrodes at opposite ends of the lamp. Softening of the lampbulb wall will then result in the heretofore mentioned expansiondiametrically which in turn results in a shortening of the overalllength of the bulb. This shortening is detected by movement of anelement in the mounting and such movement can be utilized to operate amicro-switch and thus terminate power passed to the lamp.

BRIEF DESCRIPTION OF THE DRAWING DETAILED DESCRIPTION OF THE INVENTIONReferring to the single FIGURE, there is shown a mounting means having afirst upright 11 with an adjustable set screw 12. This set screw isdesigned to support one electrode 13 at the end of an elongated lampbulb 14 including a lamp filament 15 making up a tungsten halogen lamppump for a laser system. The other electrode 16 in turn is supported bya control means in the form of an upright element 17 having an engagingportion 18. A biasing means which might constitute a simple springstructure 19 urges the engaging portion 18 against the electrode 16 sothat-a compressive force is applied along the axis of the tube. Thecontrol element 17 may be cantilevered from the base 10 in a flexiblemanner or alternatively pivoted thereto so that the force from thebiasing spring 19 will be transmitted to the lamp tube.

Above the lamp there is shown a micro-switch 20 positioned to be engagedby the control element 17 upon movement to the left as viewed in thedrawing. This microswitch in turn connects to an interlock switch system21 capable of removing power from a power supply 22 connected to thenormal light pump equipment 23. Lines 24 and 25 leading to theelectrodes l3 and 16 respectively for the lamp are shown.

OPERATION In operation, it is found that the tube wall 14 of the lampbecomes soft just preceeding failure of the lamp. Thus, by applying acompressive force along the longitudinal axis of the lamp, the physicallength dimension L will tend to shorten as the tube wall becomes soft.This shortening of the dimension results in movement of the controlelement 117 to the left and after sufficient shortening, the microswitch20 will be engaged and terminate power to the lamp. It is thus possibleto replace the lamp prior to actual failure or possible exploding of thelamp.

While the system has been described with respect to a double basedtungsten halogen lamp as might be used with a YAG laser, theprinciples-are applicable to any type of lamp in which softening of thelamp bulb walls occurs just preceeding failure of the lamp. It is onlynecessary to detect the physical change .in dimension which occurs whena force is applied to the lamp itself.

What is claimed is:

l. A method of anticipating failure of a laser lamp comprising the stepsof: detecting a change in a physical dimension of said lamp normallyoccuring just proceeding a failure of said lamp; and terminatingoperation of said lamp when said change is detected.

2. The method of claim 1, in which said lamp is an elongated doublebased tungsten halogen lamp and said detecting step includes the step ofapplying a compressive force to opposite ends of said lamp, said changein a physical dimension constituting a shortenting of the overall lengthof said lamp; and moving a control means in response to said shortening,said terminating of operation being responsive to movement of saidcontrol means.

3. A means for anticipating failure of a laser lamp wherein the lampbulb wall softens preceeding a failure, including: a mounting for saidlamp including a biasing means exerting a force on said bulb 'such thatsoftening of the bulb wall will result in a change in the physicaldimension of the lamp in the direction that said force is exerted; andmeans for detecting said change in physical dimension whereby upondetection of said change operation of said lamp can be terminated priorto failure.

4. A means according to claim 3, in which said lamp comprises anelongated tubular double based halogen lamp having electrodes at itsopposite ends, said biasing means exerting a compressive force along theaxis of said bulb at said electrodes, softening of the lamp bulb wallresulting in an expansion of the diameter of said bulb such that saidcompressing force shortens the overall length of said bulb, said meansfor detecting said change comprising an element in said mounting movablein response to said change; and a micro-switch 5 positioned to beengaged by said element upon shortening of said lamp to remove power tosaid lamp.

1. A method of anticipating failure of a laser lamp comprising the stepsof: detecting a change in a physical dimension of said lamp normallyoccuring just proceeding a failure of said lamp; and terminatingoperation of said lamp when said change is detected.
 2. The method ofclaim 1, in which said lamp is an elongated double based tungstenhalogen lamp and said detecting step includes the step of applying acompressive force to opposite ends of said lamp, said change in aphysical dimension constituting a shortenting of the overall length ofsaid lamp; and moving a control means in response to said shortening,said terminating of operation being responsive to movement of saidcontrol means.
 3. A means for anticipating failure of a laser lampwherein the lamp bulb wall softens preceeding a failure, including: amounting for said lamp including a biasing means exerting a force onsaid bulb such that softening of the bulb wall will result in a changein the physical dimension of the lamp in the direction that said forceis exerted; and means for detecting said change in physical dimensionwhereby upon detection of said change operation of said lamp can beterminated prior to failure.
 4. A means according to claim 3, in whichsaid lamp comprises an elongated tubular double based halogen lamphaving electrodes at its opposite ends, said biasing means exerting acompressive force along the axis of said bulb at said electrodes,softening of the lamp bulb wall resulting in an expansion of thediameter of said bulb such that said compressing force shortens theoverall length of said bulb, said means for detecting said changecomprising an element in said mounting movable in response to saidchange; and a micro-switch positioned to be engaged by said element uponshortening of said lamp to remove power to said lamp.